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Currently i am using JpaItemWriter to write the list of objects as below which is working fine. Now i want to change the JpaItemWriter to JdbcBatchItemWriter due to performance issue. 

    public class MyItemWriter implements ItemWriter<List<MyDomainObject>> {

    @Override  
    public void write(List<? extends Lists<MyDomainObject>> items) {
    JpaItemWriter<MyDomainObject> writer = new JpaItemWriter<>();    
    for(List<MyDomainObject> o : items)
        {
          writer.write(o);
        }
      }
    }

Suggest a sample snippets which uses the JdbcBatchItemWriter to write the List of objects will helps. Tried using the ItemSqlParameterSourceProvider it did't help ending up in org.springframework.dao.InvalidDataAccessApiUsageException: No value supplied for the SQL parameter exception

TikTik
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1 Answers1

3

You example is not correct. You are creating a JpaItemWriter in the write method, so a new instance is created on each call to write. This is probably the cause of your performance issue.

More importantly, lifecycle methods of the delegate writer (open/update/close) will not be honored (it is not the case for JpaItemWriter which does not implement ItemStream but this would be a problem if the delegate is an item stream). Your MyItemWriter implementation should be something like:

public class MyItemWriter implements ItemWriter<List<MyDomainObject>> {

   private JpaItemWriter jpaItemWriter;

   public MyItemWriter(JpaItemWriter jpaItemWriter) {
      this. jpaItemWriter = jpaItemWriter;
   }

   @Override  
   public void write(List<? extends Lists<MyDomainObject>> items) {  
     for(List<MyDomainObject> o : items) {
       this. jpaItemWriter.write(o);
     }
   }
}

Now if you want to use the JdbcBatchItemWriter to write a list of lists, see Spring Batch - Using an ItemWriter with List of Lists.

Edit: Added a sample code of how to set the delegate as requested in comments:

@Bean
public ListUnpackingItemWriter<T> itemWriter() {
    JdbcBatchItemWriter<T> jdbcBatchItemWriter = null; // configure your jdbcBatchItemWriter
    ListUnpackingItemWriter<T> listUnpackingItemWriter = new ListUnpackingItemWriter<>();
    listUnpackingItemWriter.setDelegate(jdbcBatchItemWriter);
    return listUnpackingItemWriter;
}
Mahmoud Ben Hassine
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  • Hi Hassine, thanks for your detailed information. It really helps me in understanding the code in detail. Now i am trying to follow the solution provided in https://stackoverflow.com/questions/37866312/using-an-itemwriter-with-list-of-lists but ending up in `java.lang.IllegalArgumentException: You must set a delegate!` error. Also there is no solution for this exception in that post. Can you please help in this? – TikTik Sep 05 '18 at 17:46
  • You need to call the setter `setDelegate` and set the delegate item writer you want to use. – Mahmoud Ben Hassine Sep 05 '18 at 17:58
  • I understand that, but i am bit unclear about how to set the Delegate for my specific writer. Do we have any sample snippet to look over? – TikTik Sep 05 '18 at 18:07